OFFSET
1,2
COMMENTS
Numbers k such that the multiplicative order of 2 modulo k is at its maximum possible value.
Numbers k such that the binary expansion of 1/k has period psi(n).
Write k as k = Product_{i=1..t} (p_i)^(e_i) where p_i are distinct primes. If (p_i)^(e_i) belongs to A167791 (and thus here) for 1 <= i <= t, then k is also here, but the converse is not true. In fact, this sequence has terms such that none of (p_i)^(e_i) belongs to A167791, the smallest of which is 301 = 7*43. The multiplicative order of 2 modulo 7 and 43 are 3 (< psi(7) = 6) and 14 (< psi(43) = 42), so the multiplicative order of 2 modulo 301 is lcm(3, 14) = 42 = psi(301).
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
MAPLE
select(n -> numtheory:-order(2, n)=numtheory:-lambda(n), [seq(i, i=1..1000, 2)]); # Robert Israel, Sep 12 2018
PROG
(PARI) forstep(n=1, 200, 2, if(znorder(Mod(2, n))==lcm(znstar(n)[2]), print1(n, ", ")))
CROSSREFS
KEYWORD
nonn
AUTHOR
Jianing Song, Sep 07 2018
STATUS
approved